Peanuts are susceptible to several foliar diseases, especially leaf spot, rust and net blotch. Protective fungicides are available to keep most foliar diseases at bay. 1 It is common to see some peanut plants dying throughout the season from a range of causes. Only when the plant population is significantly reduced should concern be raised. 2 Peanuts are also susceptible to several soil-borne diseases, especially Sclerotinia blight, white mould and Cylindrocladium black rot (CBR). Good rotational practices, crop management and hygiene are the best defence against these diseases. Effective fungicides are available to control the foliar diseases; however, fungicide
options are limited for control of the soil-borne diseases. 3 Conditions favouring rapid crop growth also favour the development of disease. 4 The young seedling is normally protected by the seed dressing (a fungicide). A common seedling disease in peanuts is crown rot, caused by Aspergillus niger, which is endemic in most soils. Crown rot often kills very weak seedlings and is very prevalent when soil temperatures are high. 5 Note that this is a different disease from that affecting cereal crops (caused by the Fusarium pathogen).